Pseudomonas aeruginosa
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Classification
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The genus Pseudomonas holds about sixty different types of species in the kingdom classified as bacteria. The species Pseudomonas aeruginosa is classified as a gram-negative bacterium[1]|. Most Pseudomonas aeruginosa are categorized as obligate aerobes, however sometimes in certain environmental conditions, the bacteria acts as a facultative anaerobe. Furthermore, because of the way it obtains its energy, it is considered to be a chemoheterotroph. (Willey)
Description and significance
The Pseudomonas genus includes bacteria that are straight or slightly curved rods. P. aeruginosa is a rod-shaped bacterium. Its size ranges from 0.5 to 1.0mm by 1.5 to 5.0mm in terms of its length and width. Almost all types of strains are motile by means of a polar flagellum (Todar). P. aeruginosa is a well-studied species due to its high level pathogenicity and its significant role in human disease. The organism can affect humans, animals as well as plants, and can thrive under many environmental conditions, such as in soil, water and even hospital environments. P. aeruginosa is primarily a nosocomial pathogen. According to the CDC, the overall incidence of P. aeruginosa infections in U.S. hospitals averages about 0.4 percent (4 per 1000 discharges), and the bacterium is the fourth most commonly-isolated nosocomial pathogen accounting for 10.1 percent of all hospital-acquired infections (Todar).
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
Genome structure
The genome of P. aeruginosa has an unusually large number of genes for nutrient transport, metabolic regulation and catabolism; this may be why the bacterium has the ability to grow in a wide range of environments and resist antibiotics (Willey). This microbe’s genome is a single circular chromosome that is made up of 6,264,403 base pairs (Bp), which is 6.3 million bases (Mb) and contains 5,570 predicted genes on one chromosome (Stover, et al). The P. aeruginosa almost the largest genome sequenced as compared to other bacterial genomes that have been sequenced. Due to its large genome size, P. aeruginosa has tremendous genetic density, allowing it to form biofilms. It utilizes quorum sensing (group symbiosis) to achieve its resistance against microbial agents in most cases. They also have metabolic plasmids that are about 75-230 kbp in size and are involved in degrading substances such as sugars.
Describe the size and content of the genome. Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
The P. aeruginosa has a cell wall that is gram-negative as it is composed of three layers; the plasma membrane, a thin peptidoglycan layer, and an outer membrane.
functions in protein secretions through type II and type III mechanisms to transport proteins to the outer membrane by being Sec-dependent. They are seen to have type II and type III protein secretion. Several species in the genus Pseudomonas, such as P. aeruginosa are known by their properties, which are “presence of poly-hydroxybutyrate (PHB), the production of a fluorescent pigment, pathogencity, the presence of arginine dihydrolase and glucose utilization (Willey, et al 2008).”
P. aeruginosa is ubiquitous in soil and water, and on surfaces in contact with soil or water. Its metabolism is respiratory and never fermentative, but it is able to grow in the absence of O2 if NO3 is available as a terminal electron acceptor.
they transmit aerobic respiration and complete the tricarboxylic acid cycle (TCA).
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Ecology
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Pathology
P. aeruginosa can infect animals, plants and also humans. They cause disease in humans who are already ill, infecting those patients with low resistance in their bodies. P. aeruginosa are opportunistic pathogens and cause infection in patients who are diagnosed with cystic fibrosis, have lower respiratory tract infections, surgical wounds, urinary tract infections, skin infections i.e:(dermatitis), and even in patients who have cancer i.e: blood cancer (Willey). It causes nosocomial infection in patients as this bacterium can grow anywhere where enough nutrients and enough moisture are found.
An opportunistic pathogen, P. aeruginosa produces a thick biofilm and due to its dense colonization, it is able to resist many antibiotics, disinfectants, as well as UV light and infected patients can therefore be difficult to treat. Another factor that contributes to P. aeruginosa resistance is its gram negative cell wall that is composed of three layers; the inner plasma membrane, peptidoglycan, and its outer membrane. This high level of resistance in P. aeruginosa can be of consequence and dangerous to a patient’s health.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
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References
Willey, Sherwood, Woolverton. 2008. Prescott, Harley, and Klein’s Microbiology, Seventh Edition. New York 10020: McGraw-Hill Companies, Inc. 1088p.
C.K. Stover, et al. Complete genome sequence of Pseudomonas aeruginosa PA01, an opportunistic pathogen.
Todar, Kenneth: [[Pseudomonas aeruginosa.[2]]] University of Wisconsin-Madison Department of Bacteriology.